THURSDAY, April 10, 2014 (HealthDay News) -- A series of measles cases in the United States involving children adopted from China highlights the importance of vaccinations for any adopted child from overseas, a new report reveals.

While measles was declared eliminated from the United States in 2000, cases still occur when infected people arrive in the country.

According to the U.S. Centers for Disease Control and Prevention, China is the leading source of adopted children in the United States, accounting for 30 percent of foreign-born children adopted in 2012. Measles is still a health concern in China, with a rate of just under 3 cases per 100,000 people in the first months of 2013.

The U.S. outbreaks -- occurring in Minnesota, Missouri and Washington state -- began in July 2013 when two adopted Chinese children were diagnosed with measles shortly after their arrival. Further investigation by local and state health officials identified two more measles cases, one involving a family member of one of the adopted children and another involving another newly adopted child from China.

All of the adopted children with measles were 2 years old, had cerebral palsy, and had not been vaccinated against measles, according to a team led by CDC investigator Dr. Edith Nyangoma.

Two of the adopted children had measles symptoms and were contagious while flying to the United States, potentially exposing other airline passengers and crew to measles, the CDC noted. However, follow-up investigation by health officials found that none of the other people on those flights developed measles.

Other recent U.S. outbreaks have also been caused by children adopted from overseas, including two among adopted Chinese children in 2004 and 2006, the CDC said.

Ensuring that adopted children from other countries have received all their recommended shots can prevent the spread of vaccine-preventable diseases such as measles, Nyangoma's team said.

The CDC said it is working with Chinese health officials to reduce the risk of measles being carried from China to the United States.

The study is published in the April 11 issue of the CDC journal Morbidity and Mortality Weekly Report.